Silicon nitride passivation for a solar cell

Abstract

A silicon nitride layer may be formed with a suitable refractive index, mass density, and hydrogen concentration so that the layer may serve as an ARC/passivation layer on a solar cell substrate. The silicon nitride layer may be formed on a solar cell substrate by adding a hydrogen gas diluent to a conventional precursor gas mixture during the deposition process. Alternatively, the silicon nitride layer may be formed on a solar cell substrate by using a precursor gas mixture consisting essentially of silane and nitrogen. To improve deposition chamber throughput, the silicon nitride layer may be a dual stack film that includes a low-hydrogen interface layer and a thicker bulk silicon nitride layer. Placing a plurality of solar cell substrates on a substrate carrier and transferring the substrate carrier into the deposition chamber may further enhance deposition chamber throughput.

1. A method of forming a silicon nitride layer on a solar cell substrate, comprising:
 positioning at least one solar cell substrate in a processing chamber; 
 flowing a process gas mixture into the processing chamber; and 
 generating plasma in the processing chamber to deposit a first hydrogenated silicon nitride layer on the substrate, wherein the process gas mixture includes a total precursor gas mixture and a hydrogen gas (H2) diluent, the flow rate of the hydrogen gas diluent being equal to or greater than the flow rate of the total precursor gas mixture. 
 
     
     
       2. The method of  claim 1 , wherein the total precursor gas mixture is selected from the group of gas mixtures consisting of silane (SiH 4 ) and nitrogen (N 2 ); silane, nitrogen, and ammonia (NH 3 ); and silane and ammonia. 
     
     
       3. The method of  claim 1 , wherein the positioning a solar cell substrate in a processing chamber comprises positioning the at least one substrate between first and second electrodes, the first and second electrodes being configured substantially parallel to each other. 
     
     
       4. The method of  claim 1 , wherein the generating plasma further comprises exciting the process gases with radio frequency energy having a frequency of 1-30 MHz. 
     
     
       5. The method of  claim 1 , wherein the hydrogenated silicon nitride layer contains less than about 15 atomic % hydrogen (H). 
     
     
       6. The method of  claim 5 , further comprising flowing a second process gas mixture into the processing chamber to deposit a second hydrogenated silicon nitride layer on the first hydrogenated silicon nitride layer, wherein the second process gas mixture is selected from the group of gas mixtures consisting of silane (SiH 4 ) and nitrogen (N 2 ); silane, nitrogen, and ammonia (NH 3 ); and silane and ammonia. 
     
     
       7. The method of  claim 6 , wherein the generating plasma in the processing chamber to deposit a first hydrogenated silicon nitride layer comprises generating plasma in the processing chamber to deposit a first hydrogenated silicon nitride layer having a thickness of about 10-20 nm. 
     
     
       8. The method of  claim 1 , wherein the positioning at least one solar cell substrate in a processing chamber comprises:
 placing a plurality of solar cell substrates on a substrate carrier; and 
 transferring the substrate carrier into the processing chamber. 
 
     
     
       9. A method of forming a silicon nitride layer on a solar cell substrate, comprising:
 positioning at least one solar cell substrate in a processing chamber between first and second electrodes, the first and second electrodes being configured parallel to each other; 
 flowing a process gas mixture into the processing chamber; and 
 generating plasma in the processing chamber to deposit a first hydrogenated silicon nitride layer on the substrate, wherein the process gas mixture includes a total precursor gas mixture and a hydrogen gas (H2) diluent, the flow rate of the hydrogen gas diluent being equal to or greater than the flow rate of the total precursor gas mixture. 
 
     
     
       10. The method of  claim 9 , wherein the total precursor gas mixture is selected from the group of gas mixtures consisting of silane (SiH 4 ) and nitrogen (N 2 ); silane, nitrogen, and ammonia (NH 3 ); and silane and ammonia. 
     
     
       11. The method of  claim 9 , wherein the generating plasma further comprises exciting the process gases with radio frequency energy having a frequency of 1-30 MHz. 
     
     
       12. The method of  claim 9 , wherein the first hydrogenated silicon nitride layer contains less than about 15 atomic % hydrogen (H). 
     
     
       13. The method of  claim 12 , further comprising flowing a second process gas mixture into the processing chamber to deposit a second hydrogenated silicon nitride layer on the first hydrogenated silicon nitride layer, wherein the second process gas mixture is selected from the group of gas mixtures consisting of silane (SiH 4 ) and nitrogen (N 2 ); silane, nitrogen, and ammonia (NH 3 ); and silane and ammonia. 
     
     
       14. The method of  claim 9 , wherein the positioning at least one solar cell substrate in a processing chamber comprises:
 placing a plurality of solar cell substrates on a substrate carrier; and 
 transferring the substrate carrier into the processing chamber.